Staple fiber blends



Nov. 7, 1961 s. L. MOLER 3,007,227

STAPLE FIBER BLENDS Filed April 30, 1957 fig INVENTOR GEORGE LESLIEMOLER ATTORNEY United States Patent Ofifice 3,007,227 Patented Nov. 7,1961 3,007,227 STAPLE FIBER BLENDS George Leslie Moler, Newark, Del.,assignor to E. I. du Pont de Nemours and Company, Wilmington, Del., acorporation of Delaware Filed Apr. 30, 1957, Ser. No. 656,128 25 Claims.(Cl. 2881) This invention relates to certain novel blends of two or morestaple fibers and particularly to the spinning of these blends into newand useful textile materials having improved properties.

It is conventional in the textile art to blend two different fibers inorder to achieve certain specific properties in the resulting fabrics.When two different fibers are blended, it is almost always true that thefiber present in the larger proportion will impart to the blended yarnor fabric the physical properties most characteristic of this particularfiber, whereas the physical properties inherent in the fiber present inlesser proportion will be so masked or diluted that the latterproperties will not be apparentin the yarn or fabric.

It is an object of this invention to produce novel staple fiber blendsand yarns and to prepare from these novel blends and yarns fabrics andother textile materials having a combination of improved properties notheretofore available. A further object is to produce highly stretchablefabrics having elastic properties and composed of staple yarns madefro-m a blend of a hard staple fiber with a minor proportion of asynthetic elastomeric staple fiber. Another object is to produce fabricsexhibiting the low stretch characteristic of the hard fiber componentand the high recovery of an elastomer from a blend of a hard staplefiber with a minor proportion of a synthetic elastomeric staple fiber. Astill further object is to provide a process for making a whollysynthetic fabric having elastic properties without resorting to the useof any natural rubber in the fabric. Other objects and their means ofattainment will be apparent from the following disclosure.

In its broadest aspect, the present invention comprehends a blend ofintermingled fibers of staple length comprised of a major proportion byweight of hard inelastic staple fiber and a minor proportion by weightof essentially straight elastomeric staple fiber wherein the elastomericfiber is present in an amount sufiicient to impart cohesiveness to theblend characterized by resistance to separation of the intermingledfibers and recovery upon release of separating stress, the .elastomericstaple fiber having a breaking elongation of at least 100% and anessentially complete and quick recovery from stretching to an elongationless than its breaking elongation.

In accordance with this invention there are also provided fabrics madefrom yarns composed preferably of 30% by weight of a syntheticelastomeric staple fiber and 95-70% by weight of a hard staple fiber,the elastomeric fiber preferably having between about 3 and about 12denier and a staple length of between about 0.75 and about 4.0 inches.The term elastic fiber will be used herein to refer to a syntheticelastomeric staple fiber having these dimensions. The hard staple fibermay be of any staple length or denier suitable for processing withconventional equipment. The invention also comprehends a fiber blend,sliver, card web or yarn composed of 530% by weight of the elastic fiberand 95- 70% by weight of the hard fiber, as well as woven and knittedfabrics, and batts and non-woven fabrics made therefrom.

The novel high recovery yarns of this invention may be prepared by firstblending hard staple fibers and elastic fibers to form roving, sliver,or the like and processing on conventional equipment to form a yarn.However, the spinning apparatus used must be carefully adjusted inaccordance with this invention to achieve the desired results.

In the drawing:

FIGURE 1 represents a generally schematic side view of the Saco Lowellspinning system; and

FIGURE 2 represents a schematic side view of the Casablanca spinningsystem.

The definitions of hard fiber draft zone and effective draft zone andthe operation of the process of this invention generally may be betterunderstood by reference to the drawings. FIGURE 1 represents generally aschematic side view of the Saco Lowell spinning system. A suitablestaple fiber yarn bundle (roving, sliver, or the like) is passed throughthe nip 13 of back draft rolls 2 and 3 and along apron 4 which movesabout tension pulley 5, bottom back draft roll 3, idler roll 6, and nosebar 7. The staple fiber bundle then passes under floating control roll 8which rests upon the apron and rolls by means of frictional contact withthe apron and the fiber bundle. After passing under the floating controlroll, the staple fiber bundle moves through the nip 14 of forward draftrolls 9 and 10, through pigtail 11, and is wound up with twist on bobbin12. As indicated in the drawing, floating control ro-ll 8 may be spacedat various distances y from nip 14 of forward draft rolls 9 and 10, thedistance being measured from nip 14 to the point of contact of floatingcontrol roll 8 with the fiber bundle. The distance y is termed hereinthe effective draft zone. The distance x which is the distance between.the nips of the most forward (in the direction of staple fiber bundlemovement) successive pairs of positively driven draft rolls in thespinning system is defined herein as the hard fiber draft zone.

FIGURE 2 represents a schematic side view of the Casablanca spinningsystem. A staple yarn bundle 15 is passed through the nip 29 of draftrolls 16 and 17 and then between top and bottom aprons 18 and 19,respectively. Top apron 15 passes around positively driven roll 20(pressure friction driven, gear driven, or the like) and cradle bar 21.Bottom apron 19 passes around positively driven roll 22 and cradle bar23. After leaving aprons 18 and 19, the fiber bundle passes through thenip 30 of forward draft rolls 24 and 25, through pigtail 2 6, afterwhich it is wound up as twisted yarn 27 on package 28. As indicated inFIGURE 2, the position of aprons 18 and 19 may be positionedlongitudinally along the path of movement of the fiber bundle at variousdistances from the nip 30 of forward draft rolls 24 and 25. Thisdistance is adjusted in accordance with the effects desired in the yarnproduct. The distance x between nips of the most forward successivepairs of positively driven draft rolls in the spinning system is definedherein as the hard fiber draft zone. The distance y between the nip 31formed by aprons 18 and 19 as they pass about cradle bars 21 and 23 andnip 30 is defined herein as the effective draft zone.

In the roving and drawing steps which precede the spinning step in theproduction of yarn, a draft zone is defined as the distance between twosuccessive pairs of drafting elements, and each draft zone should be setlonger than any hard or elastic fiber length entering the machine. Inthe spinning step, the hard fiber draft zone is defined as the distancebetween the nips of each successive pair of drafting elements, and eachof these hard fiber draft zones should be set longer than the length ofthe longest hard fiber entering the spinning apparatus. The effectivedraft zone (for the elastic fiber in the spinning step) is defined asthat distance from the nip of the most forward pair of drafting elementsto the closest nip of the preceding elastic fiber holding means, thelatter nip being always the most forward point where the roving is heldin contact with the spinning apron, roll, or other roving supportingmeans. This elastic fiber holding means may be in the form of anyconventional textile machinery used in drafting; such as driven rolls,floater rolls, single or double aprons, control rolls, and the like, orin other words any suitable means for holding the elastic fiber thatwill allow the next succeeding pair of drafting elements to stretch saidfiber all the way back to said holding means. No means is provided forholding the hard fiber at this point. In roving, drawing and spinningthe drafting elements referred to may comprise positively driven pairsof rolls or aprons positioned in a variety of geometrical relationshipsmoving at successively increasing speeds in order to reduce the diameterof the fiber bundle and parallelize the fibers therein.

The properties of the yarns and fabrics of this invention can beadjusted to obtain high recovery, highly elastic products on the onehand and high recovery, low stretch (hard) products on the other. Thisis especially surprising in view of the fact that all these yarns andfabrics may have the same fiber composition and are composed of only asmall proportion of elastomeric staple fiber.

The proportions of elastic fiber in the novel blends of this inventionmay vary from 5-30% by weight of total fibers in the blend. As will bemore fully understood in the examples given below, even smallproportions of the elastic fibers will result in striking improvementsin certain properties of yarns and fabrics made from these blends. Inprocessing the fiber blends on conventional textile machinery, it hasbeen found more practical to employ between and 25% of the elastic fiberin the blend, although special equipment may be selected to more readilyaccommodate broader ranges of the elastic fibers. If the proportion ofthe elastic fiber in the blend is raised sufiiciently beyond 30%, fiberprocessing operations into yarn become more difiicult to control and theresulting yarn and fabric quality suffers; for example, when 50% elasticfiber is used. However, it may sometimes be desirable to process blendsof more than 30% elastic fiber into non-woven fabrics. Regardless of theproportion of elastic fiber employed in the original blend, spun yarnsmay be woven, knitted, or otherwise processed into various fabricscontaining lower than the original proportion of elastic fiber bysuitable dilution with one or more hard fiber yarns.

The novel fiber blends of this invention may be processed into yarns andfabrics having a wide range of different properties. The stretchabilityof the yarns and fabrics is determined by the proper draft zone settingsduring spinning and is almost always independent of the proportion ofthe elastic staple fiber present in the initial blend, which is 530% byweight elastic fibers. However, two critical variables must becontrolled during spinning of the yarn. In order to prepare highstretch, high recovery yarns of this invention, the eifective draft zonemust be maintained shorter than the length of the elastic fiber beingprocessed, and the hard fiber draft zone must be maintained longer thanthe length of the hard staple fiber being processed. Unless these twodraft zone limitations are observed, optimum stretch properties are notobtained in the product. On the other hand, the same fiber blend may bespun into a yarn possessing low stretch, high recovery properties bymaintaining the effective draft zone at least as long as the length ofthe elastic fiber being processed, and the hard fiber draft zone longerthan the length of the hard fiber being processed.

Preferably, where possible, the elastic fiber length should be equal toor shorter than the hard fiber length, so that in drafting steps priorto spinning (i.e., drawing and roving), the shorter elastomer lengthswill be carried along in the processing of the blends and will notaffect processing of blends prior to spinning. For the same reason, itis preferred that the hard fiber draft zone" be longer than theeffective draft zone in spinning high stretch yarns.

Synthetic elastomeric and hard staple fibers may be blended for use inthis invention using any of the conventional textile machinery ormethods, such as hopper-fed woolen blenders, cotton pickers, blending ona Rando- Webber, card blending, blending at the draw roving or spinningframes, plying two or more yarns on a twister, or blending in theweaving or knitting step.

The fiber blends of this invention may be processed into tow, sliver,batts, yarns and other forms of textile materials on conventionaltextile machinery, so long as the drafting conditions described aboveare observed. These blends may be spun on any staple spinning system;that is, cotton, cotton American, woolen, or worsted (French orEnglish). In a typical series of fiber processing steps, the desiredproportions of elastic fiber and hard staple fiber may initially beblended on a woolen type fiber blender, processed through a cottonpicking machine to give a uniform lap, carded to open up the fibers andobtain a web and then condensed into sliver. The sliver is then putthrough conventional drafting steps of drawing, roving, and spinningwith the limitations more specifically set forth above. The resultingspun yarn may be processed further into various knitted and wovenfabrics, or the fiber blend may be converted into batts and thennon-woven fabrics, if desired.

It is preferred in processing the fiber blends in this invention tomaintain all drafting zones prior to spinning at lengths longer than thestaple fibers in the blends. although there may be special circumstancesunder which one or both drafting zones (hard fiber and effective) may beshorter than the corresponding fiber length to obtain special effects inthe resulting yarns. Prior to spinning, no stretching of the elastomericfiber normally occurs. With this arrangement it is possible to handlesliver and roving blends in the same manner as hard fiber, therebypreserving good uniformity and minimizing breaks and excessive tensionon sliver or roving.

Typical conventional drafting apparatus suitable for use with the fiberblends of this invention include double aprons of the Casablanca type(FIGURE 2) for holding the sliver or roving, as well as different rollertypes of drafting apparatus with or without floater rolls with a singleapron to hold the sliver or roving, such as is sold by Saco Lowell(FIGURE 1). Prior to spinning, the bundle of elastic and hard fibers isattenuated to form a bundle of smaller diameter without any changeeither in staple fiber diameter or length. In other words, individualfiber stretching is excluded in the drawing and roving steps. However,in the spinning step the elastic fibers in the blend are preferentiallystretched by suitable adjustment of the effective draft zone when a highstretch product is desired. When it is desired to produce a low stretchyarn, the effective draft zone in the spinning operation is adjusted sothat the elastic fibers in the blend are not intentionally stretched.

In spinning the fiber blends of this invention, it is preferred tomaintain the point of twist insertion (i.e., yarn focal point) as closeas possible to the nip of the most forward draft rolls in order toobtain the maximum permissible tension in the stretched elastic fibersas they emerge from the effective draft zone, or in other words toobtain the maximum stretch possible in the yarns produced. This means ineffect that the yarn spinning tension will be higher and travelerweights slightly heavier than normally used when processing wholly hardfiber yarns. It will be obvious to those skilled in the art, however,that this yarn focal point may be adjusted if desired to produce avariety of properties in the yarns and fabrics produced; i.e., changesin tactile hand, visual appearance, bulk, and the like. In the case ofvery fine yarns, the yarn spinning tension will still be greater thanwhat is conventional for hard fiber yarns and yet the traveler may be ofcustomary weight. In addition, when spinning any one staple blend onidentical spinning equipment with constant effective and over-all draftzones, the following variables affect staple yarn elasticity asindicated:

(1) At constant yarn twist multiplier, increasing cotton count increasesyarn elasticity.

(2) At constant yarn twist, increasing cotton count (i.e., decreasingtwist multiplier) decreases yarn elasticity.

(3) At constant cotton count, increasing yarn twist (i.e., increasingtwist multiplier) increases yarn elasticity.

(4) Yarn elasticity varies directly with floater roll weight.

In plying, yarn elasticity initially decreases rapidly with addition ofopposite direction ply twist (e.g., Z in singles, S in ply), then levelsoff as balanced ply twist is approached, and then the elasticityincreases gradually as further twist is added.

One of the important features of this invention is the provision offiber blends which permit the manufacture of high recovery yarns andfabrics having a wide range of stretchability from low stretch to highstretch properties. For example, it is now possible for the first timeto prepare a wide range of light weight to heavy weight staple fiberfabrics which have the appearance, tactile hand, cover and comfort ofconventional staple fabrics plus high recovery and stretch properties asdesired. There have not been available heretofore light weight elasticfabrics having the above composition or combination of properties. Bysuitable adjustment of the composition and drafting procedure inaccordance with this invention, a wide variety of elastic textilematerials may be produced in addition to various high recovery textilematerials having certain other advantages. The stretchy yarns have muchhigher bulk than those yarns made from 100% of the same hard fiber, andthe stretchy yarns of this invention may be made without many of theconventional processing steps required heretofore to produce stretchycontinuous filament yams; e.g., without the need for specializeddrawing, covering, twisting, crimping, heat setting, or shrinking.

The significant distinction between the blends of this invention havinghigh stretch properties and those having low stretch properties is thatin the case of the blends having high stretch, the elastomer fiber isthe load-bearing member during extension, whereas in the case of blendshaving low stretch properties the hard fiber is the loadbearing memberduring the extension part of the cycle. During the recovery part of thecycle, the elastomer fiber is the major factor contributing to the highdegree of recovery exhibited in both types of products. The terms highstretch and low stretch are terms employed to compare the stretchproperties of the Yarns and fabrics of this invention relative to thestretch properties of the yarns or fabrics of the same constructioncontaining only hard fibers. In other words, a fabric prepared from ablend of elastic and hard fibers and spun with the correct criticaleffective draft zone setting for producing high stretch propertiesexhibits a Stretchability higher than that of the same fabricconstruction prepared from 100% hard fibers. By adjusting the draft zonesetting to produce a fabric having low stretch properties, there isobtained a fabric which stretches the same order of magnitude as thestretch in a 100% hard fiber control fabric, although of course thefabric containing the elastic fiber possesses a higher recovery than thecontrol fabric.

Examples of suitable elastic or stretchy products of this inventioninclude woven, knitted and non-woven fabrics for use in universalfitting apparel (socks, polo shirts, underwear, bathing suits, gloves,elastic cuffs, sweaters, waistbands, suits, coats, dresses, skirts,action sportswear, leotard-type outerwear, and accessories such astapes, webbings and other woven, non-woven, or knit apparel fabrics),household products (form-fitting upholstery, slip covers, sheets,carpets, mattress coverings, and narrow tapes and webbings for a widevariety of uses), industrial products (transportation upholstery, wovenand non-woven felts, tapes and webbings for varied applications), andmedical products (surgical bandages, supports, elastic dressings,surgical stockings, and splint tapes).

Low stretch, high recovery fabrics of this invention may be made intoouter-apparel (sweaters, knit jersey, and woven, knit, or non-wovensuitings and dress goods), household items (rugs, carpets andupholstery) and industrial products (woven, non-woven, and knitcompression or impact bearing structures).

In the case of low stretch, high recovery products, the imposition of anexternal stress causes the fabric to deform, within the limit of fabricconstruction, to the limit of the load-bearing hard fibers present inthe fabric. The elastomer fiber component, being a low modulus material,does not aid in this deformation. Therefore, in uses where it isdesirable that the fabric resist stretching (i.e., elongation) uponapplication of external stress, the low stretch group of products tendsto retain their shape. However, upon release of the applied stress theelastomer fiber comes into play and contributes to a higher degree ofrecovery in the blend or fabric (i.e., super-recovery) than is possiblewhen the elastomer is not present.

The hard inelastic staple fiber used in this invention may be any hardstaple fiber suitable for processing on conventional textile equipment.The term inelastic as used herein is intended to apply to any fiberhaving relatively low stretch characteristics as compared to the stretchcharacteristics of the elastic fibers disclosed herein. The hardinelastic staple fiber may be prepared from any synthetic fiber-formingmaterials, such as polyesters (e.g., polyethylene terephthalate),polyamides (e.g., polyhexamethylene adipamide, polyhexamethylenesebacamide, polycaproarnide, and copolymers of various amides), acrylicpolymers and copolymers (e.g., polyacrylonitrile, copolymers ofacrylonitrile with vinyl chloride, vinylidene cyanide, vinyl pyridine,methyl acrylate), vinyl polymers (e.g., vinyl chloride/vinyl acetatecopolymer), polymers and copolymers of tetrafluoroethylene,monochlorotrifiuoroethylene, and hexafiuoropropylene, polyethylene,cellulose derivatives (e.g., cellulose acetate, regenerated cellulose,ethyl cellulose, cellulose triacetate), glass, or from any naturalfiber, such as cotton, wool, silk, jute, linen, or a blend of two ormore hard fibers.

The term elastic as used herein has the meaning conventionally given tothat term in the art and is applied herein to describe a syntheticelastomeric staple fiber capable of at least 100% elongation beforebreaking. Elastic fibers utilized in this invention preferably willundergo between about 500% and about 800% elongation before breaking andhave a modulus (force required to stretch to a specified elongation) ofabout 0.05 gram per denier or less. This is in contrast to hard fiberswhich are generally characterized by a modulus between about 18 andabout grams per denier and which usually will stretch no more than about20-40% before breaking. The elastic fibers of this invention are notonly characterized by very high Stretchability but also by very quickrecovery (almost instantaneous) to the original uncrimped condition.Stretchability of the elastic fiber does not depend upon crimping ortwisting.

The elastic fiber utilized in this invention may be any syntheticelastomeric staple fiber having a denier between about 3 and about 30and a staple length between about 4 inch and about 4 inches. Acondensation elastomer will usually form fibers having a tensile formrecovery above about 75% and a stress decay below about 35% whenmeasured by two test procedures described below. Segmented elastomers,which comprise the broadest class of polymers meeting theserequirements, are prepared by starting with a low molecular weightpolymer (i.e., one having a molecular weight in the range from about 700to about 3500), preferably a difunctional polymer with terminal groupscontaining active hydrogen, and reacting it with a small co-reactivemolecule under conditions such that a new difunctional intermediate isobtained with terminal groups capable of reacting with active hydrogen.These intermediates are then coupled or chain-extended by reacting withcompounds containing active hydrogen. The low molecular weight startingpolymer may be a polyester or polyesteramide and the co-reactive smallmolecule is a diisocyanate. A large variety of co-reactive hydrogencompounds may be used in preparing the segmented condensationelastomers. Among the most practical chainextending agents are water,diamines, and dibasic acids.

US. 2,692,873 describes similar products in which the startingpolyesters have been replaced by polyethers of a corresponding molecularweight range. A number of macro-molecular compounds, such aspolyhydrocarbons, polyamides, polyurethanes, etc., with suitablemolecular weights, melting point characteristics, and terminal groups,can serve as the starting point for preparing segmented elastomers ofthis type. The diisocyanate may be replaced with other difunctionalcompounds, such as diacid halides, which are capable of reacting withactive hydrogen. Elastic copolyether ester fibers are obtained bycondensation of a polyether glycol, an aliphatic glycol, and an aromaticdibasic acid, or suitable derivative and forming a fiber from thepolymer. Use of a fiber of an elastomer of this type is illustrated inthe examples.

Fibers of other types of condensation elastomers are also suitable. US.2,670,267 describes N-alkyl-substituted copolyamides which are highlyelastic and have a suitable low modulus. A copolyamide of this type,obtained by reacting adipic acid with a mixture of hexamethylenediamine,N-isobutylhexamethylenediamine, and N,N'- isobutylhexamethylenediamine,produces an elastomer which is particularly satisfactory for thepurposes of this invention. US. 2,623,033 describes linear elasticcopolyesters prepared by reacting glycols with a mixture of aromatic andacyclic dicarboxy-lic acids. Copolymers prepared from ethylene glycol,terephthalic acid, and sebacic acid have been found to be particularlyuseful. Another class of useful condensation elastomers is described inUS. 2,430,860. The elastic polyamides of this patent are produced byreacting polycarbonamides with formaldehyde.

Elastic fibers having the proper denier and length as described aboveand prepared from fiber-forming addition polymer such as, for example,copolymers of butadiene/ styrene, but-adiene/acrylonitrile andbutadiene/Z- vinyl pyridine, polychlorobutadiene, copolymers ofisobutylene with small proportions of butadiene, chlorosulfonatedpolyethylene, copolymers of monochlorotrifiuoroethylene with vinylidenefluoride, and the like, may be employed.

The fiber blends, yarns, fabrics, and other textile products prepared inaccordance with this invention may be given the customary finishingtreatments where necessary or desired, such as scouring, washing,drying, pressing, dyeing, heat-treating, and softening.

The following examples illustrate specific embodiments of this inventionfor preparing high stretch, high recovery products as well as lowstretch, high recovery products. All proportions are by Weight unlessotherwise specified.

EXAMPLE I A blend of acrylic staple fibers and copolyester elastomerstaple fibers is used to prepare a sweater having high recoveryproperties. The blend contains (1) 30% of a staple fiber (2 inches long,2 denier per filament, drawn 4 formed from a copolymer of 94%acrylonitrile and 6% methyl acrylate and having a residual shrinkage ofabout 15%, (2) 45% of the same acrylic staple fiber but having aresidual shrinkage of about 2%, and (3) 25% of copolyetheresterelastomer staple fiber (1 /2 inches long and 3 denier per filament). Thecopolyetherester fiber is composed of 40% ethylene glycol terephthalateand 60% tetramethylene oxide glycol terephthalate. The three fibers aresprayed with 1% of a suitable lubricating and antistatic finish, thensandwichblended, made into laps on a cotton picker, carded into sliver,drawn, then converted into roving. The roving is spun into an 18.5/1cotton count yarn (10 Z twist) and 2-plied 5 S. In all draft zones inthe aforementioned processing steps, both the effective and the hardfiber draft zones are set longer than any of the staple fibers in theblend. The yarn is knit into a sweater at 13 courses per inch on a 12cut, 36 gauge, 17 inch, 4 feed Jacquard sweater body machine. A controlyarn of 100% acrylic fibers (2 inches long, 2 denier per filament, 70%of which have 2% residual shrinkage and 30% of which have 15% residualshrinkage) is knit into a sweater on the same machine, also at 13courses per inch. Both knitted fabrics are boiled off under relaxedconditions and then steamed in a relaxed condition for 30 seconds toremove wrinkles. subjectively, the fabric containing thecopolyetherester elastomer fiber felt much softer and had better cover,compression and bounce than the control fabric containing no elastomerfiber. Table I shows that the fabric recovery properties of the fabriccontaining the small proportion of elastomer staple was substantiallysuperior to the control fabric.

A blend of staple fibers containing 50% polyacrylonitrile staple fiber(1 /2 inches long, 3 denier per filament and drawn about 4 and 50%elastomer staple fiber (6 denier, 1 /2 inches long) made from acopolyester of 40% poly(ethylene oxide) terephthalate and 60% ethyleneterephthalate is prepared on a small card and fed into a commercialsynthetic-fur knitting machine. Staple fibers (1 /2 inches long, 3denier per filament) of 100% poly-acrylonitrile are treated similarly asa control. The test blend and control are then sheared to simulate amouton fur. Subjectively, the test sample feels softer tactily than the100% conventional hard fiber control. Compressional recovery data showthat the fur containing 50% elastomer is substantially superior to thecontrol, as indicated in Table II.

A woven fabric useful for dress goods is prepared using the followingfilling and warp yarns:

Test filling yarn:

% polyhexamethylene adipamide staple (3 denier per filament and 2 incheslong) 20% copolyetherester elastomer staple (same as Ex.

I except 6 denier per filament) Finish applied to both staplesCotton-American system Yarn count: 25/2 cc.

Twist:

Singles 25 2 Ply 12 8 Test warp yarn:

100% polyhexamethylene adipamide (3 denier per filament and 1 /2 incheslong) Finish applied Cotton-American system Yarn count: 20/2 cc.

Twist:

Singles 20 2 Ply 12 8 Plain weave fabrics (30 warp and 36 filling) arewoven from y-arns Spun on a Whitin Casablanca spinning frame with a hardfiber draft zone set at 4 inches and effective draft zone set at inch.All draft zones prior to spinning are set longer than any of the staplefibers in the blend.

A control fabric of the same weave and count is prepared on the samemachines from 100% polyamide staple fibers (1 /2 inches long and 3denier per filament in the warp yarn and 2 inches long and 3 denier perfilament in the filling yarn).

Weave: Plain Loom count: 30 warp x 36 filling Control warp yarn:Identical to test Warp yarn Control filling yarn: Identical to testfilling y-arn except made from 100% polyamide Table III Control TestFabric Fabric Tensile Recovery (percent) 25% Elongation 41 78 EXAMPLE IVA blend of staple fibers is prepared containing (1) 60% acrylic staple(2 denier per filament and 2 inches long) having a residual shrinkage ofabout 2%, (2) 25% acrylic staple (3 denier per filament and 2 incheslong) having a residual shrinkage of about 15%, and (3) 15% elasticcopolymer fiber (6 denier per filament and 1 /2 inches long), The twoacrylic staple fibers are the same as those used in Example I. Theelastic copolymer is prepared by condensing poly(tetramethy1ene oxide)glycol (40 parts) having a molecular weight of 1,000 with 20 parts ofmethylene bis(4-phenylisocyanate). The polyether diurethane havingisocyanate terminal groups is reacted with 2 grams of hydrazinemonohydrate in N,N-dimethylformamide to produce a copolymer with aninherent viscosity of 2,2 in m-cresol solution. Filaments are dry spunfrom this copolymer and cut to the designated staple length.

Two percent of a lubricating and antistatic finish is sprayed on each ofthe fibers. The three fibers are blended on a woolen blender andprocessed via Cotton- American system as follows: 2 passes Whitinpicker, roller carded, 2 passes drawing frame (Saco Lowell), 1 passroving frame (Saco Lowell). At this point, the

10 roving is split into two separate lots for processing on Saco Lowellspinning frame (FIGURE 1). All draft zones prior to spinning are set ata distance longer than any of the staple fibers in the blend.

Lot A is spun with draft rolls set as follows:

Inches Hard fiber draft zone 3% Effective draft zone 1% A low stretch,conventional appearing, high recovery 18/1 cotton count sweater yarn isproduced from an over-all spinning draft of 14X.

Lot B is spun with draft rolls. set as follows:

Inches Hard fiber draft zone 3% Effective draft zone /2 high recoveryand high stretch.

Table IV Low High Stretch Stretch Yarn, Lot Yarn, Lot A B Cotton CountlS/2 30/2 Twist Multipliersingles 2. 4 3. 3 Twist Multiplier2 ply 1. 62. 3 Twist Multiplier-Rama. 3/2 3/2 Tenacity (grams per denier) 1. 4 1.4 Percent Stretchability:

As-spun 2. 3 56 Boiled Ofi 9. 8 140 Percent Recovery from stretchAs-spun 92 77 Boiled Off 82 A control yarn spun under the sameconditions as lot A is prepared from a blend of 60% 3 denier perfilament, 2 inch acrylic staple (2% residual shrinkage) and 40% 3 denierper filament, 2 inch acrylic staple (15% residual shrinkage), bothacrylic staple having the same composition a that in Example I.

Two sweaters were knit on a 12-cut Lieghton Transfer machine, one fromlot A low stretch, superior recovery yarn and one from the acryliccontrol yarn. The test sweater and control sweater were dyed beige andfinished simultaneously by commercial procedures to produce a finishedcourse x wale construction of 18 x 16. When compared with the controlsweater, the test sweater showed substantially improved tensilerecovery, indicative of better shape retention in the body, neckband,waistband and sleeve cuffs of the sweater. In addition, the test sweatercontaining elastic fiber requires only half the loading force of thatrequired by the control sweater in order to stretch it widthwise (coursedirection) by 50%. This reflects the superior ease of putting on thetest sweater as well as the improved comfort of this garment over abroader range of body dimensions than the control sweater will satisfy.Also, the test sweater has a softer more cashmere-like hand than thecontrol sweater.

EXAMPLE V A series of seven yarns of different fiber composition asshown in Table V are prepared using essentially the same conditions asthose described for the yarn of Example III. The effective draft zonesfor spinning yarns E, F, and G are set shorter than the length of theelastic copolymer fiber in each blend. After spinning, all yarns arescoured 30 minutes in carbon tetrachloride, then boiled off 30 minutesin water containing 1% wetting agent, and dried.

11 Yarn bulk is determined for each sample of yarn at the two loadsgiven in Table V. The table shows that yarns made from blends of hardfiber and elastic fiber (i.e., yarns D, E, F, and G) have superior bulkwhether spun 12 passes drawing frame (Saco-Lowell), 2 passes rovingframe (Saco-Lowell). Drawing roll settings are l-2=3", 23=2 and rovingroll settings are 12=2%, 23= All draft zone settings prior to spinningare into high stretch or low stretch yarns, as compared with 1 on erthan eith r fib n th lend. S n in s done corresponding control yarnscontaining no elastic fiber. e er 1 e b In H g 1 Table V Yarn BulkNominal (cc/gm.) 1 Sample Composition Yarn Type Count (Taut) At 0.1 At0.5 gm. load gm. load Cotton Conventional 40/1 1.54 1.41 100%lowshrinkage acrylic fibcr (Ex. I) .do 25/2 3.65 3. 36 00% of B and 40%high shrinkage acrylic fiber 18/2 6. 90 5. 98

Ex. 60% of B, 25% high shrinkage acrylic fibcr Low Stretch 18/2 7.487.01

(Ex. I) and copolymer fiber (Ex. IV). Same as D High Stretch 30/2 8. 837. 81 85% cotton and 15% copolymer fiber (Ex. IV) do 40/1 5. 36 2.96 80%cotton and copolymor fiber (Ex. IV). 40/1 5. 79 4. 45

1 Cubic centimeters per gram.

EXAMPLE VI One end of roving (2 hank) prepared as in Example IV from ablend of 60% low shrinkage acrylic fiber, high shrinkage acrylic fiberand 15% elastic fiber, and two ends of roving (4 hank) composed of ablend of 80% (2 d.p.f., 2 /2 inches) and 20% (4 /2 d.p.f., 2 /2 inches)acrylic staple fibers of Example I (both having a residual shrinkage ofabout 2%) are fed simultaneously to a Saco-Lowell spinning frame. Themachine settings for spinning are as follows:

Hard fiber draft zone 3% (longer than hard fiber). Effective draft zone/1 (shorter than elastic fiber).

Draft 17.2X.

Twist 19 Z.

Traveler #24.

As shown in Table VI, a high stretch 17/1 cc. yarn containing 92.5%acrylic fiber and 7.5% elastic fiber was produced from this blend. Thishigh stretch yarn was particularly useful for knitting into mens halfhose. Without the elastic staple fiber or the proper effective draftzone setting, a high stretch yarn is not produced, as shown in Table VI.

EXAMPLE VII This example illustrates how a high stretch yarn containing20% elastic fiber may be diluted by weaving into a fabric containing aslittle as 4% elastic fiber while imparting high recovery and highstretch to the fabric.

A blend is prepared from 80% (2 d.p.f., 2 inches) acrylic staple fibermade from the same compositions as described in Example I and having aresidual shrinkage of about 2%, and 20% (6 d.p.f., 2 4 inches) elasticstaple fiber made from the same elastic copolymer composition as thatdescribed in Example IV.

A suitable lubricating and antistatic finish is applied to both fibers.The elastic fiber is given a preliminary opening and then blended withthe acrylic fiber on a woolen blender and processed on a Cotton-Americansystem as follows: 2 passes Whitin picker, roller carded, 2

on a Saco-Lowell spinning frame with the following settings:

Hard fiber draft zone 3" Effective draft zone Draft 20.4X Twist 30 ZTraveler #23 These settings produce a high stretch 40/ 1 cotton countyarn which is then two-plied 10 S. This yarn has 1.4 grams per deniertenacity and 234% stretchability with 86% recovery after relaxation(boiled off). The yarn is dyed yellow in skein form.

Fabrics are then woven utilizing this yarn and a control yarn identicalto the 100% acrylic control yarn of Example IV as filling yarns in a 75denier black acetate warp.

FABRIC I Warp75 denier black acetate (commercial yarn) Filling-270denier (40/ 2 cotton count) stretchy yellow yarn (20% elastic fiber)Loom construction-180 ends x 50 picks Weave-5 shaft satin FABRIC IIWarp75 denier black acetate (commercial yarn) Fillings:

(A) 270 denier (40/ 2 cotton count) stretchy yellow yarn (B) 550 denier(18/2 cotton count) acrylic control yarn (undyed) Loom constructionlends x 50 picks Weave5 shaft satin, alternating 20 picks of A with 20picks of B.

The fabrics are given a crab scour at 140 F. in water and detergent, pintenter dried at 250 F. relaxed, semidecated for 3 minutes steam andvacuumed one minute. Finished fabric I weighs 7.2 oz./yd. and has handstretch. Finished fabric II weighs 10 oZ./yd. and has 5060% handstretch. Both fabrics exhibit high recovery and high stretchcharacteristics making them especially suitable for use as bathingsuits, sheath-type dresses and upholstery slip-covers. The compositionof fabric I is 40% acrylic/50% acetate/ 10% elastic copolymer, whilethat of fabric II is 56% acrylic/40% acetate/ 4% elastic copolymer.Bothfabrics have a tensile form recovery from 50% elongation of 88%. Bymixing various proportions of high stretch yarns with low stretch yarns,fabrics having different surface textures may be achieved. For example,fabric I described above is fiat and smooth in appearance while fabricII is alternating puckered and flat stripes.

13 EXAMPLE VIII Two non-woven felts are prepared, one from rabbit furand the other from a mixture of fur and a synthetic elastic copolymer.Before felting, each fiber is opened up and blended by hand carding. Thefur or fiber blend is felted by feeding the staple fibers to a standardAbbott felting machine which simultaneously works the fibersmechanically while applying heat and moisture for the cycles indicatedbelow.

Sample A consists of 75% by weight of rabbit fur blended with 25% byweight of 3 d.p.f., /2 inch% inch elastorner fiber, said elastomer fiberbeing the same composition as the elastic copolymer fiber described inExample IV. This blend of fur and elastic copolymer is processed wet inthe Abbott felting machine for 10 minutes at 70 C. Sample B consists of100% rabbit fur and is used as a control, this fur being processed wetin the Abbott felting machine for minutes at 55 C. followed by alO-minute cycle at 51 C. Sample A upon testing shows a felt density of0..23 gram per cc., whereas sample B shows a density of 0.16 gram percc. In comparing qualitatively the delamination tendencies of the twofelts, sample A shows no delamination, whereas sample B shows a slighttendency to delaminate on flexmg.

The relative delamination tendencies of the two felts show that theelastic copolymer does not inhibit felting as most synthetic fibers do,but actually enhances the felting of the fur. Addition of the elasticcopolymer to the fur increases the density and therefore the hardnessand compactness of the felt structure. Of significant importance is thefact that none of the felt structures containing the elastic copolymershows any tendency to delaminate, which is a common fault with mostblends of fur with synthetic hard fibers processed by normal feltingtechniques of heat, moisture, and mechanical working. It should be notedthat even the 100% fur felt shows slight delamination under the testconditions and that this tendency is eliminated by addition of elasticcopolymer to the fur.

EXAMPLE 13;

Several samples of staple fibers are taken from the card slivers duringprocessing of the staple, and these samples are shaped by hand into astaple pellet'and subjected to the Busse compressional recovery test.

Since the Busse test correlates pile retention with re covery, thesedata are indicative of the improvement which an elastic fibercontributes in crush resistance and recovery performance of rugs, furs,felts, stufling, and any other non-woven structure where the staplefibers are compressed together or bent tightly upon one another andrecovery from this condition is desirable.

There follows a description of each test used in the examples to measurethe designated properties of blends, yarns, and fabrics.

The breaking tenacity in grams per denier is the tensile stress of ayarn specimen at rupture. This value is measured on a Suter tensiletester. All yarn samples are conditioned and tested at 65% relativehumidity and 70 F. The gauge length of the specimen is inches. The yarnsample vismounted at the specified gauge length under approximately 0.1gram per denier load and the 14 lower jaw of the tester is dropped at arate of 12 inches per minute.

The tensile form recovery is the recovered elongation expressed as apercentage of the imparted elongation for fibers, yarns, and fabrics.This property is measured on fabrics for example, using an Instrontensile tester using test specimens which are 1 inch wide and allowing agauge length of 1 inch between the jaws of the tester. All fabricsamples are moisture conditioned and tested at 65% relative humidity and70 F. All elongation rates for the samples are per minute. The testspecimen is mechanically conditioned by elongating it by 10% of itsoriginal length and then allowing it to recover immediately beforetesting. The specimen is then extended the designated percentelongation, held at that elongation for one minute and then allowed torecover at the same rate as it was extended.

The stress decay of the fiber, yarn, or fabric is determined using thesame apparatus as described above for determining tensile form recoveryemploying the same test samples. During the period the textile sample isheld at the specified elongation for one minute as outlined in the abovetest, the force necessary to maintain this elongation changes with time.The ratio of this incremental change in force to the original forcenecessary to obtain the specified elongation, expressed as a percentage,is designated as the stress decay of the sample.

The yarn bulk in cc./gm. is the equivalent of the specific volume of ayarn which is equal to the inverse of the yarn density in gm./cc. Themeasurement is carried out at 65 relative humidity and 70 F. The averageyarn diameter is measured optically under the designated loads. Theaverage yarn weight is measured under the same loads. By knowing thelength of yarn used, the specific volume or bulk is then calculated incc./gm. of the yarn at the designated loads.

The recovery from dead-weight compression in percent is the ability of apile type structure to recover from a crushing load. The test is carriedout at 65% relative humidity at 70 F. A pressure of 15 p.s.i. is appliedto the test specimen on a flat horizontal surface for 18 hours. Thepressure is then removed and the specimen thickness is measured after adesignated recovery time (48 hours), and the recovery is expressed as apercentage of the original specimen thickness. All thicknessmeasurements are made with an Ames gauge at 0.32 p.s.i.g.

The stretchability of a yarn and the recovery of a yarn, both expressedas percent, are a measure of the ability of a yarn to extend or stretchunder a designated load (force) and recover from such stretching. Theyarn is prepared (as-spun or boiled-01f) in skeins by winding the yarnat a load of approximately 0.1 gram per denier (g.p.d.). The number ofturns per skein equals yarn denier This gives a total denier of 10,000forthe yarn bundle when skeins are suspended from two-gram hooks andanother two-gram hook is added to the bottom loop of each skein. Theinitial skein length is designated IL. A weight of 1,000 grams isadded'to the bottom hook on the skein for 30 seconds. As close to theend of the 30- second interval as possible, the extended skein length ismeasured and designated EL. The 1,000-gram weight is removed, leavingthe two-gram hook on the skein, and the skein is permitted to recoverfor 15 minutes. The recovered skein length is designated RL. Thefollowing calculations are then made:

Percent stretohability (at 0.1 g.p.d. load) X 100 EL RL Percent recoveryfrom stretch 100 15 The felt density is a measure of the weight per unitvolume in grams per cubic centimeter of' the felt which indicates itscompactness and hardness. The density is vcalculated from the thicknessof the sample, measured at 3.2 psi. with an Ames gauge, and the weightper unit area of the felt.

The delamination tendency of the felt sample is a qualitative rating ofthe tendency of the felt to separate into layers when flexed by hand asif the fibers were merely placed together in a temporarily compactedmass without true interlocking of the fiber structure.

The Busse compressional recovery test measures the ability of a pelletor plug of staple fibers to recover from compressional forces and isexpressed in percent. The apparatus used in the Busse test is describedin Textile Research Journal, 23, 84 (1953). The test is performed at 65%relative humidity and at 70 F. A tuft of staple fibers weighing 0.3 gramis taken from a sliver or batt and placed in a metal cylinder which is0.2 square inch in area. The tuft of staple is formed into a loosepellet by compressing it with a light wooden rod at approximately 0.2p.s.i. The initial height of the loose pellet is then measured underthis load. The wooden rod is then replaced with a steel rod and aloading force of 1,000 p.s.i. is applied to the pellet for one minute.This compressed pellet of fiber is then removed from the cylinder andallowed to recover for designated time intervals. The recovery inpercent at these time intervals is calculated from the ratio of therecovered pellet height to the initial pellet height. Because of theremoval of the rod before the final measurement, the recovery may begreater in some cases than the initial height.

The claimed invention:

1. A blend of intermingled fibers of staple length comprising a majorproportion by weight of a hard inelastic staple fiber, and a minorproportion by weight of essentially straight synthetic elastomericstaple fiber, said elastomeric fiber being present in an amountsufficient to impart cohesiveness to said blend characterized byresistance to separation of said intermingled fibers and recovery uponrelease of separating stress, said elastomeric fiber having a breakingelongation of at least 100% and an essentially complete and quickrecovery from stretching to an elongation less than its breakingelongation, said synthetic elastomeric staple fiber having a denier ofless than about 30.

2. The staple fiber blend of claim 1 in the form of a fabric.

3. The staple fiber blend of claim 1 in the form of a non-woven fabric.

4. The staple fiber blend of claim 1 in the form of a woven fabric.

5. The staple fiber blend of claim 1 in the form of a high stretch wovenfabric.

6. The fiber blend of claim 1 in the form of a strand.

7. The fiber blend of claim 1 in the form of a high recovery, highstretch yarn.

8. The fiber blend of claim 1 wherein said elastomeric fiber is asegmented elastomer having a tensile recovery above about 75% and astress decay below about 35% 9. The fiber blend of claim 1 wherein saidelastomeric staple fiber is present in said blend in an amount fromabout to about 30% by weight of said blend.

10. The fiber blend of claim 9 wherein said elastomeric staple fiber hasa length between about inch and about 4 inches and is present in anamount from about to about 25% by weight of said blend.

11. A cohesive blend of intermingled fibers of staple length comprisingfrom about 95% to about 70% by weight of a hard inelastic staple fiber,and from about 5% to about 30% by weight of essentially straightsynthetic elastomeric staple fiber having a breaking elongation of atleast 100%, a denier between about 3 and about 30, a stretch modulussubstantially less than said hard fiber, and an essentially complete andquick recovery from stretching to an elongation less than its breakingelongation.

12. A fiber blend of claim 11 wherein said elastomeric fiber issegmented elastomer having a tensile recovery above about 75% and astress decay below about 35%.

13. The fiber blend of claim 11 wherein said elastomeric fiber has abreaking elongation of at least about 500% and a stretch modulus of upto about 0.05 gram per denier.

14. The fiber blend of claim 12 wherein said elastomeric fiber is apolyurethane fiber.

15. A fiber blend of claim 11 wherein said hard inelastic staple fiberhas a stretch modulus of from about 18 to about grams per denier and abreaking elongation not greater than about 40%.

16. A spun staple fiber yarn composed of a blend of 70% by weight ofhard inelastic staple fiber, and 530% by weight of essentially straightelastic synthetic elastomeric staple fiber having a length between aboutinch and about 4 inches, a denier between about 3 and about 30, astretch modulus of up to about 0.05 gram per denier and highstretchability characterized by an elongation before breaking of atleast combined with an essentially complete and quick recovery fromstretching to an elongation less than its breaking elongationindependent of effects due to crimping and twisting, the elastomericfibers being stretch positioned relative to the hard fibers to provide ayarn of controlled stretchability and high recovery from stretchingwherein the hard fibers become load bearing to limit the amount ofstretch before reaching said break elongation of the elastomeric fiberswhen tension is applied to the yarn, and wherein the hard fibers becomebulked by said recovery of the elastomeric fibers when tension on theyarn is released.

17. A yarn as defined in claim 16 wherein the length of the hard fibersis at least equal to that of the elastomeric fibers.

18. A yarn as defined in claim 16 wherein the elastomeric fibers have anelongation between about 500% and about 800% before breaking.

19. A yarn as defined in claim 16 wherein the elastomeric fibers have atensile form recovery above about 75% and a stress decay below about 35%from 100% elongation.

20. A yarn as defined in claim 16 wherein the yarn has a tensile formrecovery of at least 70% from 50% elongation when tested in the form offabric.

21. A yarn as defined in claim 16 wherein the yarn has at least 56%stretchability at 0.1 gram per denier load and at least 77% recoveryfrom stretch.

22. The yarn of claim 16 wherein said hard inelastic staple fiber has astretch modulus of from about 18 to about 85 grams per denier and abreaking elongation not greater than about 40%.

23. A high recovery, high stretch yarn comprised of a blend ofintermingled fibers of staple length comprising a major proportion byweight of a hard inelastic staple fiber, and a minor proportion ofessentially straight synthetic elastomeric staple fiber having abreaking elongation of at least 100%, an essentially complete and quickrecovery from stretching to an elongation less than its breakingelongation, a length of at least inch and a denier from about 3 to about30, said elastomeric fiber being stretch positioned in said yarn andbeing present in an amount sufiicient to provide high recovery fromstretching.

24. The yarn of claim 23 wherein said elastomeric staple fiber ispresent in an amount from about 5% to about 30% by weight of said blend.

25. The yarn of claim 23 wherein said hard inelastic staple fiber has astretch modulus of from about 18 to about 85 grams per denier and abreaking elongation not greater than about 40%.

(References on following page) References Cited in the file of thispatent UNITED STATES PATENTS Carothers Sept. 20, 1938 Boeddinghaus Nov.21, 1939 Miles Apr. 23, 1940 Waterman et a1. Apr. 30, 1940 Hardy Oct. 8,1940 Simpson Feb. 4, 1941 Wallach Aug. 19, 1941 18 Dreyfus Jan. 27, 1942Bell et a1 June 27, 1944 Truitt June 4, 1946 Cairns Nov. 18, 1947Schneider May 4, 1948 Harris et a1 Apr. 18, 1950 Rickus July 10, 1951Goeppel Aug. 4, 1953 Speakman et a1. Oct. 26, 1954

1. A BLEND OF ITERMINGLED FIBERS OF STAPLE LENGTH COMPRISING A MAJORPORPORTON BY WEIGHT OF A HARD INELASTIC STAPLE FIBER, AND A MINORPORPORTION BY WEIGHT OF ESSENTIALLY STRAIGHT SYNTHETIC ELASTOMERICSTAPLE FIBER, SAID ELASTOMERIC FIBER BEING PRESENT IN AN AMOUNTSUFFICIENT TO IMPART COHENSIVENESS TO SAID BLEND CHARACTRIZED BYRESISTANCE TO SEPARATION OF SAID INTERMINGLED FIBERS AND RECOVERY UPONRELEASE OF SEPERATING STRESS, SAID ELASTOMERIC FIBER HAVING A BREAKINGELONGATION OF AT LEAST 100% AND AN ESSENTIALLY COMPLETE AND QUICKRECOVERY FROM STRETCHING TO AN ELONGATION LESS THAN ITS BREAKINGELONGATION, SAID SYNETHIC ELASTOMERIC STAPLE FIBER HAVING A DENIER OFLESS THAN ABOUT 30.